The present invention is related to U.S. Pat. application Ser. No. 07/363,749 filed on June 9, 1989 entitled "Floatation Chamber For Use In A Chest Drainage Device" assigned to a common assignee Sherwood Medical Company and incorporated herein by reference. The present invention relates to an improvement over the prior application wherein the operational range of a chest drainage device constructed according to the present invention may be increased.
Chest drainage devices for removing fluids from the pleural cavity of a patient generally include a collection chamber, a water seal chamber and a suction control chamber. The suction control chamber operates to limit the negative pressure applied to the collection chamber and the pleural cavity of the patient. During the operation of a chest drainage device, liquid from the patient's pleural cavity is drawn into and accumulated in the collection chamber. Gases are drawn from the pleural cavity of the patient and pass through a water seal in the water seal chamber to the source of suction. The water seal operates as a barrier to prevent the patient's pleural cavity from being exposed to the atmosphere and also prevents the patient's pleural cavity from being in direct flow of communication with the vacuum source.
U.S. Pat. No. 3,783,870, issued to Schachet on Jan. 8, 1974, and U.S. Pat. No. 4,439,190, issued to Protzmann et al on Mar. 27, 1984 describe the operation of a typical chest drainage device, both of which are incorporated herein by reference. The present invention is readily adaptable for use in an integral one-piece chest drainage device or a multi-bottle chest drainage device similar to the chest drainage devices referenced above. Generally, the suction control chamber allows the user to apply a prescribed vacuum pressure to the pleural cavity of a patient by adding a predetermined amount of liquid to the suction control chamber. The commonly used chest drainage device utilizes a suction control chamber which is basically an unequal-legged water manometer to regulate the suction pressure being applied to the pleural cavity of a patient. This type of suction control chamber generally consists of a pair of legs or columns interconnected at their bottom ends. The top of the generally smaller, first column, is open to the atmosphere. The second column is generally larger than the first column and includes a top end in flow communication with the vacuum source and the pleural cavity of the patient.
The overall height of the suction control chamber typically dictates the minimum height of the chest drainage device. Commonly available chest drainage devices have an overall height of approximately 40 cm. In the typical suction control chamber, approximately 25 cm. is attributable to the operational range of the chest drainage device. The remaining height of the chest drainage device is attributable to the air/water separation space located above the water fill level and the height of the base or stand of the chest drainage device.
The effectiveness of the air/water separation space at any given air flow rate is determined by the over all suction control chamber geometry and the height of the suction control chamber above the liquid level. If the air flow rate through the suction control chamber is too high, liquid is entrained in the air and will be carried out of the suction control chamber. If this occurs, the vacuum pressure being applied to pleural cavity of the patient will gradually decrease as the liquid level in the suction control chamber is depleted. Additionally, the liquid from the suction control chamber may contaminate the vacuum source and/or be deposited within other chambers of the chest drainage device. Certain chest drainage devices have incorporated baffles in the top of the suction control chamber in an effort to decrease the required height of the air/water separation space and to prevent the loss of water in the suction control chamber.
In a chest drainage device, the pressure applied to the pleural cavity of the patient is dependent on the dynamic water height of the liquid in the suction control chamber. For example, if the desired patient pressure is 20 cm. H.sub.2 O of vacuum pressure, a dynamic water height of at least 20 cm. is required in the suction control chamber. In chest drainage devices which utilize a water seal chamber, the water seal chamber will typically add approximately 2 cm. H.sub.2 O of resistance so that if the desired patient pressure is 20 cm. H.sub.2 O, the suction control chamber must provide 22 cm. H.sub.2 O of vacuum pressure to overcome the resistance of the water seal chamber. The standard operating ranges for most chest drainage devices is between 5 and 25 cm. H.sub.2 O vacuum pressure. Therefore, in order to have the capability of supplying 25 cm. H.sub.2 O of vacuum pressure to the pleural cavity of the patient, this portion of the suction control chamber must be at least 25 cm. high. The baffle systems used in certain chest drainage devices are designed to prevent liquid from being entrained in the air and may be used to reduce the height of the air/water separation space and do not materially effect the dynamic water height of the suction control chamber. Therefore, unless valves or other flow restricting devices are used, the height of a chest drainage device must be at least 25 cm. plus the height of the air/water space or baffle chamber and the base of the chest drainage device.